The mechanism by which a specific stimulus at the platelet membrane is translated within the cell to the varied responses will be investigated. The intracellular messengers, such as Ca ions, cAMP and prostaglandin intermediates, will be related to the induction of aggregation and secretion by various stimuli. The mechanism of regulation of phosphorylase will be studied to better understand metabolic control associated with stimulation of platelets. BIBLIOGRAPHIC REFERENCE: Charo, I.F., R.D. Feinman, and T.C. Detwiler, Inhibition of platelet secretion by an antagonist of intracellular Ca 2 ion. Biochem. Biophys. Resch. Commun. 72. 1462 (1976).